1. Field of the Invention
The invention relates generally to integrated circuits, more particularly to storage of analog signals.
2. Description of Related Art
In the field of non-volatile analog signal storage, one focus of existing solutions has been on high-density storage, such as arrays of cells. Another focus of existing solutions has been in the area of high-speed programming algorithms. The objective in both instances is to provide techniques useful for commercial memory products that compete against traditional types of digital memories, such as EPROM""s, EEPROM""s and FLASH memories, which are extremely dense and may be programmed in a very straightforward manner. Consequently, the conventional cells are not optimized for extremely high accuracy, especially over time varying conditions such as power supply and temperature fluctuations.
Conventional solutions in the field of voltage references focus mainly on bandgap designs or shunt regulators using zener diodes. However, both of these techniques have fundamental limitations with regard to temperature performance. Moreover, both have difficulty working at very low power supply levels ( less than 1.5V).
Accordingly, it is desirable to have a structure and method for providing a non-volatile analog signal storage for a precision voltage reference.
The invention discloses a programmable and non-volatile analog signal storage structure and method that employ two non-volatile cells which are arranged as a differential transistor pair. The non-volatile transistor at the positive (or non-inverting) terminal of the amplifier is referred to as the reference cell, while the non-volatile transistor on the negative (or inverting) input of the amplifier is referred to as the storage cell. The structure comprises an analog storage unit that produces a voltage that is independent of temperature and supply voltage variation. Additionally, the circuit structure is capable of operating at low supply voltage levels ( less than 1.5V).
An integrated circuit for storing analog signals comprises a differential amplifier configuration including a storage unit having: a NV (non-volatile) storage cell (M3); and a NV (non-volatile) reference cell (M4), coupled to the NV storage cell, wherein the NV storage cell and the NV reference cell form a differential pair in the differential amplifier configuration.
Advantageously, the present invention attains a high degree of accuracy in a non-volatile analog storage medium, such as EEPROM.
This summary does not purport to define the invention. The invention is defined by the claims.